Field of the Invention and Related Art Statement
The present invention relates to a TV system conversion apparatus provided for converting numbers of picture frames and scanning lines of a television picture signal, particularly, for facilitating the mitigation of deterioration of picture quality such as ambiguity and judder which is caused in plural motional portions of a picture in company with the system conversion.
In a conventional type TV system conversion apparatus provided for converting a television picture signal of M line/N field system into that of different K line/L field system, the spatio-temporal linear processing of a picture signal is effected through an interpolation filter 1 and a thinning circuit 2, as shown in FIG. 1, so as to convert numbers of picture fields per second and scanning lines. For example, when an input TV picture signal of field number N system of fields per second N=60 is converted into an output TV picture signal of field number L system of fields per second L=50, a conversion period during which 6 fields of Nos. 1 to 6 of the input picture signal are converted into 5 fields of Nos. "a" to "e" of the output picture signal is provided, as shown in FIG. 2. In this exemplified conversion of the number of picture fields, when the picture signal linear processing for obtaining a weighted average of two continued fields of the input picture signal is effected, so as to form a new field of the output picture signal which is situated between those two continued fields, such a serious defect is brought out that, if the picture is motional, the positions of the picture in those two continued fields prepared for obtaining the weighted average thereof are shifted from each other, and hence the ambiguity and the judder are caused in edge positions of the picture and the conspicuous deterioration of picture quality results therefrom.
The above described defect is necessarily caused by the aforesaid conventional simple linear interpolation. Meanwhile, in "a TV system conversion system" as proposed in the specification of Japanese patent application No. 244,638/84, which was filed by the same applicants as the present application, a remarkable improvement of the above defect caused in ordinary TV pictures can be obtained by the interpolation effected after the shifted positions of the picture are compensated in response to the detection of the motion of picture and the motion vector. In fact, the most of ordinary TV pictures contain only simple motions such as generated by panning and tilting which are effected for following a specified target, so that fair effects can be obtained by the above picture processing. However, in a situation where plural motional portions, which are comparatively noticeable and present individual motions being different from each other, are contained in the same TV picture, a further defect such as the effect of improvement of picture quality can not be sufficiently obtained is brought out from the above described prior picture processing.